As a related-art apparatus of this type of technology, in Patent Literature 1, there is disclosed an electric power steering apparatus configured to determine that a torque signal of a torque sensor is abnormal when such a situation continues for a given time period or longer that an absolute value of the torque signal is smaller than a predetermined value in the vicinity of zero, a steering speed of a steering wheel (that is, a rotation speed of a load) is equal to or larger than a given value, and a steering angle (that is, a rotation angle of the load) is in an increasing direction, and detect an abnormality based on a kind of consistency between the torque signal of the torque sensor and a rotation state.
Further, in Patent Literature 2, there is similarly disclosed an electric power steering apparatus configured to apply an instantaneous motor torque for abnormality detection, and detect an abnormality in a sensor signal of a torque sensor when the application of the instantaneous motor torque is not reflected in the sensor signal of the torque sensor.
As an example of another general and basic apparatus, there exists the one that includes two systems for each sensor to detect an abnormality in each sensor through mutual comparison therebetween. For example, the apparatus includes two-system torque detecting units and detects an abnormality occurring in the torque detecting unit of any one of the systems through mutual comparison therebetween. Some apparatus also include two-system rotation-state detecting units.